1. Field of the Invention
The present invention relates to an azimuth propeller device. More specifically, the present invention relates to an azimuth propeller device including a motor for driving a POD propeller.
2. Description of Related Art
In general, a conventional ship is provided with a propeller and a rudder separately provided with the propeller, which are attached to the stern of the ship so that the driving force for the ship is exerted by the propeller, and operations, such as turning of the ship, are performed by the rudder.
Recently, however, the propeller used for driving the ship and the rudder used for operating the ship are integrated, and an azimuth propeller device, simply called an azimuth propeller, which is attached to the ship to be rotatable in the vertical direction of the ship, has been developed.
The structure of a conventional azimuth propeller device will be briefly described with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram showing an attachment of an azimuth propeller device at the stern portion of a ship. FIG. 4A is a diagram showing a partial cross-sectional view of the right hand side of the azimuth propeller device. FIG. 4B is a diagram showing a cross-sectional view of the azimuth propeller device shown in FIG. 4A taken along the line Axe2x80x94A. In the figures, the numeral 1 indicates a rear portion of the ship""s bottom, 2 indicates an azimuth pod, 3 indicates a shaft, 4 indicates a current plate member, 5 indicates a POD propeller member, 6 indicates a propeller shaft, 7 indicates a stator, 8 indicates a rotor, 9 indicates a motor, and 10 indicates an azimuth propeller device.
As shown in the figures, the azimuth propeller device 10 is rotatably attached to the rear portion of the ship""s bottom 1 via the shaft 3. The azimuth propeller device 10 includes the POD propeller member 5, the azimuth pod 2, and the current plate member 4. The POD propeller member 5, which exerts the driving force for the ship, may be attached to the front or back of the azimuth propeller device 10. The azimuth pod 2 accommodates a propeller drive mechanism, such as the motor 9, on the inside thereof The current plate member 4 is integrally fixed to the upper portion of the azimuth pod 2 and has a streamline cross sectional shape. The current plate member 4 is attached to the lower portion of the shaft 3 which extends in the vertical direction, and the upper portion of the shaft 3 is coupled with a driving mechanism (not shown in the figures), which is disposed in the hull so that the shaft 3, the current plate member 4, the azimuth pod 2, and the POD propeller member 5 are integrally rotated.
By using the azimuth propeller device 10 having the above mentioned structure, it becomes possible to drive the ship using the driving force generated by rotating the POD propeller member 5, and to obtain steering function by rotating the azimuth propeller device 10 with respect to the rear portion of the ship""s bottom 1 to change the travelling course of the ship.
Note that there are two types for the azimuth propeller device 10. One in which the motor 9 for outputting a driving force for the POD propeller 5 is disposed in the azimuth pod 2 as shown in FIG. 4A, and the other in which a driving force is received from a driving source (not shown in the figures), such as a motor, disposed in the hull. The azimuth propeller device 10 shown in FIGS. 4A and 4B has a structure in which the rotor 8 is rotated together with the propeller shaft 6 with respect to the stator 7, which is fixed to the inside wall of the hollow azimuth pod 2. In order to handle the heat generated by driving the motor 9, an air-cooling system, in which cooling air supplied into the azimuth pod 2 from the hull is circulated, is adopted for the conventional azimuth propeller device 10.
For the above-mentioned air-cooling system for the azimuth propeller device, however, since it forcibly circulates the cooling air, a number of components become necessary, such as a supply source of the cooling air, a passage for the cooling air, an impelling means such as a fan for the cooling air, and a driving source for actuating the impelling means. For this reason, it becomes necessary, from the viewpoint of structure, to secure space for installing the passage, the impelling means, etc., in at least one of the azimuth propeller device and the hull. Accordingly, this is disadvantageous in terms of decreasing the size or cost of the azimuth propeller device. In addition, since power is consumed for the cooling system, the running cost is also increased.
The present invention takes into consideration the above-mentioned circumstances, and has as an object to provide an azimuth propeller device which is capable of completely eliminating the necessity of cooling the motor, etc., using the air-cooling system or keeping it down to a minimum level.
In order to achieve the above object, the present invention provides an azimuth propeller device including an azimuth pod, a POD propeller member provided with the azimuth pod, a motor which drives the POD propeller member, the motor being provided inside the azimuth pod, and at least one radiation member provided with an outer periphery of the azimuth pod.
In accordance with another aspect of the present invention, the radiation member is a fin extending in the front and back direction of the azimuth pod.
In yet another aspect of the present invention, the fin is twisted in the rotation direction of the POD propeller member from the front to back of the fin.
According to the above azimuth propeller device, since at least one radiation member is provided with the outer periphery of the azimuth pod, it becomes possible to effectively release the heat which is generated by the rotation of the motor inside the azimuth pod into the surrounding water via the radiation member. That is, it becomes possible to effectively carry out a water-cooling operation using water of the ocean, a river, a lake, etc., in which the ship is traveling, and hence the air cooling operation can be eliminated or decreased to a minimum level. Accordingly, it has a remarkable effect a reduction in the size and cost of the azimuth propeller device.
Also, since at least one of the fins extending in the front and back direction of the azimuth pod is adopted as a radiation member, it becomes possible to secure a large heat transfer area to improve the radiation efficiency.
Moreover, since the fin is twisted in the rotation direction of the POD propeller member from front to back of the fin, a water flow adjusting effect can be obtained in addition to the above-mentioned radiation effect. Accordingly, the present invention can also contribute to improvement in driving force.